Field of the Invention
The invention pertains to the field of optical short-circuit plugs which are especially used for the diagnosis and/or self-testing of optical devices (i.e. sender/receiver modules (Transceivers) or optical cables) before or after their installation. A short-circuit plug can cause an intended, optical damping or attenuation which may be adjustable, if necessary. A further function of short-circuit plugs lies in the protection of optical devices against external influences, especially during transport and installation.
The invention relates to an optical short-circuit plug for short-circuiting two optical units, especially the sender and receiver unit of a sender/receiver module, having a short-circuit optical waveguide, and two plug pins which are separate elements and which accommodate respective ends of the short-circuit optical waveguide for coupling to the optical unit.
A short-circuit plug which is known from U.S. Pat. No. 5,076,688 includes a short-circuit optical waveguide and a solid plastic housing which is formed by complete remolding of the short-circuit optical waveguide in a single molding process. The plug pins which accommodate the short-circuit optical waveguides are thereby formed as integral components of the plastic housing. The short-circuit optical waveguide must be surrounded by a multi-layer metal protective coating in order to protect the injection casting material. The short-circuit plug is a reproduction of a connection plug which is couplable to the transceiver in normal operation.
The short-circuit plug is comparatively costly and requires a relatively high amount of injection casting material because of the solid housing. Furthermore, the spacing of the plug pins is fixed and inflexible. The coupling relationships can only be comparatively inaccurately reproduced due to the lack of defined coupling forces of the plug pins.
The last-mentioned problematic, improved short-circuit plugs of the above-mentioned type, in which the ends of a short-circuit optical waveguide for coupling to the optical units are accommodated by a plug pin that is constructed as a separate element, are known from U.S. Pat. Nos. 4,952,798 and 4,982,083. The plug pins respectively include a middle region with an axially adjustable flange, which supports a helical spring. Another end of each helical spring bears against a disc which is respectively fixed to the back end of the plug pin. In that construction, the individual plug pins are displaceably disposed counter to the respective pressure of the helical spring. The plug pins can carry out a tilting movement around their central region, in order to equalize the tolerances with regard to their radial spacing.
With regard to their spring characteristic, the known short-circuit plugs require relatively precisely manufactured helical springs which are relatively costly to handle as loose material. Due to the tilting movement, the equalization of radial spacing tolerances leads to an inhomogeneous load and oblique position of the plug pins.